There is an increasing interest to derive compounds from biomass that may be used as fuel components in gasoline, jet fuel, or diesel fuels. For instance, ethanol is currently produced at large scale as a fuel component for gasoline. Ethanol is presently allowed to be blended into gasoline at a maximum of ten percent of the volume of the resulting gasoline fuel. Higher concentrations of ethanol are likely to cause corrosion issues for vehicles that were not designed for high ethanol fuels such as E85 (eighty-five percent ethanol and fifteen percent hydrocarbon based gasoline). Most gasoline fuel sold in the US includes ethanol.
Biodiesel, as obtained from the transesterification of vegetable oils and animal fats, is a common blending component of diesel fuel and may legally and technically be added is high proportions. However, only low concentration blends of biodiesel-in-diesel are currently used due in part to the limited availability of biodiesel feedstocks. Renewable diesel is another biofuel that can be blended with diesel in high concentrations and is made from vegetable oils and animal fats. Renewable diesel faces the same limitations as biodiesel in terms of feedstock availability.
It is highly desirable to use lignocellulosic biomass (the most abundant form of biomass on the planet) as a source of fuel components for diesel. However, little success has been achieved in transforming lignocellulose components, i.e. lignin and carbohydrates for the most part, into compounds that can be used in blends with diesel. This lack of success is due in part to the nature of lignocellulose fractions. Lignin, for instance, makes for about 5-30% of plant biomass (lignocellulose). Lignin is a tri-dimensional, highly branched aromatic polymer with mainly ether-type linkages whose aromatic functions are single phenyl rings. Lignin is particularly difficult to process into compounds that could be used as transportation fuel components and, thus far, there is no commercial technology that converts lignin into fuel components. The other lignocellulose fraction, the carbohydrate fraction (70-95%), is mainly composed of cellulose and hemicellulose. These carbohydrates are biopolymers whose polymeric units are single sugars with five to six carbon atoms. Such sugar units are joined through glycosidic bonds, i.e., C—O—C bonds. When carbohydrates are thermally or biochemically processed for fuel applications, the products are oxygenates or hydrocarbons with two to six carbon atoms. These types of compounds (e.g. ethanol, butanol, pentane, hexane, and others) are suitable for gasoline blending, but they do not fulfill specifications for diesel blending. Thus, there is an opportunity for technologies that are able to convert carbohydrates (cellulose and hemicellulose, and corn starch and sugar cane carbohydrates) into compounds fungible with diesel fuel that meet diesel fuel characteristics.